The use of stents, and other implantable medical devices such as grafts, stent-grafts, vena cava filters, etc, hereinafter referred to cumulatively as stents, to maintain the patency of bodily lumens is well known.
Stents are typically delivered via a catheter in an unexpanded configuration to a desired bodily location. Once at the desired bodily location, the stent is expanded and implanted in the bodily lumen.
Typically, a stent will have an unexpanded (closed) diameter for placement and an expanded (opened) diameter after placement in the vessel or the duct. Some stents are self-expanding; some stents are expanded mechanically with radial outward force from within the stent, as by inflation of a balloon; and some stents, known as hybrid stents, have one or more characteristics common to both self-expanding and mechanically expandable stents.
An example of a mechanically expandable stent and associated delivery system is shown in U.S. Pat. No. 4,733,665 to Palmaz, which issued Mar. 29, 1988, and discloses a number of stent configurations for implantation with the aid of a catheter. The catheter includes an arrangement wherein a balloon inside the stent is inflated to expand the stent by plastically deforming it, after positioning it within a blood vessel.
A type of self-expanding stent is described in U.S. Pat. No. 4,503,569 to Dotter which issued Mar. 12, 1985, and discloses a shape memory stent which expands to an implanted configuration with a change in temperature. Self-expanding stents are constructed from a wide variety of materials including nitinol, spring steel, shape-memory polymers, etc.
In many stent delivery systems, particularly those used to deliver a self-expanding stent, the stent is typically retained on the catheter via a retention device such as a sheath. The stent may be deployed by retracting the sheath from over the stent. To prevent the stent from being drawn longitudinally with the retracting sheath, many delivery systems provide the catheter shaft with one or more bumpers or hubs.
However it is known that in many cases when a sheath is withdrawn from a stent, particularly a self-expanding stent constructed of shape memory material, the stent may be displaced longitudinally relative to the catheter shaft as a result of so-called “stent jumping,” wherein when a sleeve or sheath is withdrawn from the stent during delivery the stent frictional forces and stent constrainment forces exerted by the retracting sleeve on the stent are less than those of the stent expansion force at an angle exiting the stent delivery system. As a result, in some instances, as the sheath is withdrawn from about the stent, the stent will tend to migrate or “jump” longitudinally relative to the stent mounting region of the catheter resulting in the imprecise delivery of the stent and/or distortion of the stent body. Because a portion of the stent is already expanding beyond the diameter of the catheter when stent jumping typically occurs, the presence of one or more hubs on the catheter shaft will typically not prevent stent jumping.
It would thus be desirable to provide a stent delivery system and/or one or more components thereof which may reduce or eliminate occurrences of stent jumping in order to improve the accuracy of stent placement within a vessel or other body space.
All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
Without limiting the scope of the invention a brief summary of some of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.
A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims.